CHORDATES

Question 1

Subphyla

Answer 1

• Cephalochordata (lancelets)
• Urochordata (sea squirts)
• Craniata (all vertebrates)

Question 2

What is thought to be the sister clade to Echinodermata before the Chordates?

Answer 2

• Hemichordata (the Acorn worms)

Question 3

Describe the two superclasses of Craniata

Answer 3

• Gnathostoma ( lampreys, jawless fish )

- Agnatha ( all jawed vertebrates )

Question 4

What are their key characteristics?

Answer 4

1) pharyngeal gill slits
2) notochord
3) dorsal nervous cord
4) post anal tail
5) bilateral symmetry
6) segmentation

Question 5

Segmentation is distinct in the ____.

Answer 5

notochord

Question 6

What does it mean when we say a reversal in the top-bottom axis? Same ___ control this

Answer 6

ancestral state shows the heart and vessels dorsally and notochord ventrally, however this has now been flipped

• genes .

Question 7

Which 2 chordate traits do urochordata (sea squirts) show?

Answer 7

• pharyngeal gill basket

- post anal tail

Question 8

What is different functionally about the Cephalocordata (lancelets) gill slits? They also show obvious notochord ____.

What provides them with longitudinal stiffness?

How are muscles arranged?

Answer 8

• used for filter feeding not O2 absorption
• segmentation
• supporting notochord structure
• myotomal blocks

Question 9

Characteristics of the Gnathostomata

Answer 9

• share all chordate characterisits
• notochord replaced with more advanced bony skeleton
• brain protected by an elaborate brain case and cranium
• gill bars and pharynx evolve new structures for gas exchange
• in some very advanced cases, the anterior gill bar is modified into a jaw
• diverged into elongate form and armoured

Question 10

AGNATHA Living jawless fish are the ___ and the hagfish. These are usually ___ as adults and have retained ____.

Answer 10

a) lampreys
b) parasitic
c) notochord

Question 11

What were the Ostracoderms?

Why have bone on outside?

Answer 11

the first armoured, jawless fish

• protection
• insulation of electrophoretic organs
• storage of minerals

Question 12

Fish teeth are derived from __ in bony fish and dermal scales in ___ fish.

Answer 12

a) papilla

b) cartilaginous

Question 13

3 shared characteristics of jawed fish

Answer 13

• muscles organised into myotomes
• paired pelvic and pectoral
• notochord replaced with cartilage or bone